1. Field of the Invention
This invention relates to a velocity observer electronic control circuit and an imbalance observer electronic control circuit for an active magnetic damper or bearing.
2. Description of The Prior Art
In order to destabilize the journals in the magnetic field of an attractive type active magnetic bearing and/or damper, control feedback of both the journal displacement and velocity are necessary. In the prior art generally, the displacement has been measured and has been processed by a differentiator or phase-lead circuit to achieve the velocity information. However, the process of differentiation tends to be noisy and unreliable.
Japanese Patent Nos. 57-65415 (A) and 57-65416 (A) differ from the prior art in applying a feedback control current based on integration rather than differentiation. These two Japanese patents are similar in that their reason for applying the current integration feedback was to eliminate the "position drift". This has the effect of making the bearing statically stiff. However, both patents describe circuits which have a separate phase compensation element which indicates that the current integration itself does not provide for phase compensation. The main difference between the two patents is that the latter one provides control of two opposite coils instead of one.